Weyl Nodal Line-Surface Half-metal in CaFeO$_3$

TL;DR

This paper predicts a novel spin-polarized semimetal state in CaFeO$_3$ featuring Weyl nodal lines and surfaces, which is robust and promising for spintronics applications.

Contribution

It introduces a fully spin-polarized Weyl nodal line-surface half-metal state in CaFeO$_3$, based on first-principles calculations and symmetry analysis, highlighting its robustness and potential applications.

Findings

Identifies Weyl nodal line-surface states in CaFeO$_3$

States these states are protected by specific symmetries

Shows robustness against strain and correlation effects

Abstract

Manipulating the spin degrees of freedom of electrons affords an excellent platform for exploring novel quantum states in condensed-matter physics and material science. Based on first-principles calculations and analysis of crystal symmetries, we propose a fully spin-polarized composite semimetal state, which is combined with the one-dimensional nodal lines and two-dimensional nodal surfaces, in the half-metal material CaFeO$_3$. In the nodal line-surface states, the Baguenaudier-like nodal lines feature six rings linked together, which are protected by the three independent symmetry operations:$\mathcal{PT}$, $\mathcal{M}_{y}$, and $\mathcal{\widetilde{M}}_{z}$. Near the Fermi level, the spin-polarized nodal surface states are guaranteed by the joint operation $\mathcal{T}\mathcal{S}_{2i}$ in the $k_{i(i=x,y,z)}=\pi$ plane. Furthermore, high-quality CaFeO$_3$ harbors ultra-clean energy dispersion, which is rather robust against strong triaxial compressional strain and correlation effect. The realization of the Weyl nodal line-surface half-metal presents great potential for spintronics applications with high speed and low power consumption.